In recent years, in order to highly efficiently reduce a discharge amount of harmful materials such as NOx and to flexibly handle a variation in power consumption per day, for example, as introduced in Patent Document 1 corresponding to the application of the present applicant, a single shaft combined plant having one directly-connected shaft is used. The single shaft combined plant performs an engagement or disengagement operation of a gas turbine and a steam turbine to a generator in accordance with an occasional demand through an automatic self-aligning engagement clutch (hereinafter, simply referred to as an SSS clutch) using a helical spline engagement structure and called an SSS (Synchro Self Shifting) clutch. An example of such a structure and an operation thereof is introduced in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-013709).
In this kind of single shaft combined plant, for example, during a start operation, the steam turbine is driven by steam generated by the operation of the gas turbine. For this reason, first, the gas turbine is operated while the steam turbine is in an idle state. When steam is generated, the steam turbine is operated. Accordingly, a driving shaft of the steam turbine may be connected to the generator through the SSS clutch almost at a rated rpm. Alternatively, the steam turbine may be stopped when the power demand is small at nighttime, and may be operated and connected to the generator through the SSS clutch when the power demand is large at daytime.
However, in this kind of single shaft combined plant with such a configuration, a variation occurs in a ground having the plant installed thereon due to a variation in age or an earthquake, and an axis displacement may occur between the shaft of the gas turbine and the shaft of the steam turbine. In addition, as described above, the gas turbine is started first during the start operation, and then the steam turbine is started. However, since the gas turbine is rotated at a rated rpm for a long time, a bearing support base of the SSS clutch on the side of the gas turbine is expanded due to a high drain oil temperature of a bearing. On the contrary, since an expansion rate of a bearing support base of the SSS clutch on the side of the steam turbine is different in accordance with the state of the steam turbine, an axis displacement occurs between the shaft of the gas turbine and the shaft of the steam turbine. In addition, a difference in slope or a difference in uplift occurs between the shaft of the gas turbine and the shaft of the steam turbine.
For this reason, when the generator, the gas turbine, and the steam turbine engage with each other through the SSS clutch, when the amount of the axis displacement between the shaft of the gas turbine and the shaft of the steam turbine becomes a value larger than a predetermined specified value, the engagement operation of the SSS clutch is performed in the state where all the gas turbine, the generator, and the steam turbine are rotated almost at a rated rpm. For this reason, an excessive stress is applied to the SSS clutch. As a result, the clutch may be damaged.
Therefore, it is necessary to periodically measure the amount of the axis displacement, but it is difficult to check the amount of the axis displacement during an operation. Thus, the peripheral parts of the corresponding part are disassembled in the state where the operation is stopped. Then, for example, a rotor of the generator is rotated by a hand, and a measurement operation of the amount of the axis displacement needs to be performed by using a dial gauge or the like. However, in such a measurement operation, since it takes time to disassemble the peripheral parts of the corresponding part and to perform the measurement operation of the amount of the axis displacement, a cost involved therewith is required.
For this reason, for example, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-106738), the present applicant has proposed an axis displacement measuring apparatus, an axis displacement measuring method, a single shaft combined plant using the axis displacement measuring apparatus, and a method of starting the single shaft combined plant which measure an amount of an axis displacement upon performing an engagement operation of the SSS clutch during an operation by using various sensors such as a temperature sensor for obtaining an expansion amount using a temperature of each of bearing support bases supporting driving shaft bearings on both sides of the SSS clutch, a gap measuring sensor for calculating a slope of a shaft by measuring a gap between an upper fixed point of the shaft and a lower fixed point thereof, and a gap measuring sensor provided at plural points in the circumferential direction of the bearing so as to obtain an amount of an axis displacement.
However, in the single shaft combined plant disclosed in Patent Document 1, the axis displacement detection operation for detecting whether the normal engagement operation of the SSS clutch is performed is not mentioned. In addition, in the axis displacement measuring method disclosed in Patent Document 2, since plural temperature sensors or gap measuring sensors are required, a cost involved therewith is required. Also, since the measurement operation is indirectly performed by calculating the amount of the axis displacement on the basis of the measurement result of the sensors, a calculation error may occur due to a data conversion.
For this reason, an object of the invention is to provide a method of detecting an amount of an axis displacement in a power transmission device using an automatic self-aligning engagement clutch, the method being capable of directly and accurately detecting the amount of the axis displacement in the automatic self-aligning engagement clutch during an operation with a simple configuration.